Human cytomegalovirus (HCMV) is a highly prevalent herpesvirus efficiently transmitted by transfusion or transplantation. Sterilization techniques through leukoreduction and pathogen inactivation techniques (e.g., psoralen/UVA) are available but the development of HCMV-safe cellular therapies for transplantation requires more sophisticated strategies. As part of a long-term goal to devise strategies that rely on reducing viral control of cell death, this proposal explores the role of the viral cell death suppression gene, UL36, in HCMV growth in macrophages, with the objective of validating UL36 as a target for selectively suppressing HCMV in cellular therapy components. Monocytes and the macrophages derived from them are highly likely target cells for this manipulation based on the following: 1) progenitors of granulocytes, macrophages, and dendritic cells (GM-Ps) are important contributors to HCMV transmission because they harbor latent virus that serves as the source for infection, 2) differentiation of these progenitors to macrophages allows for lytic growth of the virus, and 3) growth in macrophages is considered to be a critical step for HCMV transmission and ensuing disease. The murine CMV (MCMV) UL36 homolog, M36, is essential for replication in macrophages, and it is anticipated that UL36 in HCMV will also be essential for growth in macrophages. It is anticipated that properties of UL36, binding procaspase-8 and preventing activation, also makes it an attractive target during the differentiation process that yields permissive cells because this protease is important in monocytes undergoing macrophage differentiation as well as during apoptosis. Further, novel cell death suppression functions encoded by the UL36 gene have been uncovered that expand the anticipated role of this gene in this important cell type. Long-term goals will be initiated and immediate goals addressed in two specific aims designed to 1) determine the contribution of differential splicing to UL36 gene function in macrophages, and 2) determine the contribution of the microRNA miR 36-1 to UL36 gene function in macrophages. Recombinant viruses and robust, transfection-based strategies will be incorporated in a focused effort to identify the UL36 gene products that inhibit multiple cell death pathways deployed by macrophages to inhibit HCMV replication. PUBLIC HEALTH RELEVANCE: Human cytomegalovirus (CMV) is a highly prevalent herpes virus that causes life- threatening disease, especially following blood transfusions, transplantations, or if it is transmitted to an unborn child. The development of CMV-safe cellular therapies for transplantation requires novel approaches;the development of these strategies will likely indicate effective means of preventing transmission in other situations. This proposal will determine viral mechanisms that prevent intrinsic defenses that kill infected cells important to disease transmission.